This invention relates to the field of equipment for particulate treatment of surfaces. More specifically, it relates to the field of equipment for subjecting parts to sand blast, shot blast or similar blasting operations to effect cleaning, preening, or similar surface treatments. Typically, precision cast parts are subjected to a shot blast to remove burrs and casting imperfections. Such operations are accomplished in an enclosed chamber into which the shot is thrown at high velocity by centrifugal throwing wheels or air pressure. In order to treat a large number of such articles, it is desirable to have the blast treatment process be a continuous one to avoid the necessity for frequently loading and unloading the blast cabinet. To that end finger seals have been developed which permit the entry and exit of parts from a blast cabinet on a continuous basis while at the same time substantially preventing the particulate from escaping the cabinet and potentially injuring a worker.
Finger seals of the type herein disclosed are of a flexible construction and are secured over an opening to the blast cabinet. By using a plurality of such seals the entire opening can be covered. The seals are secured at their top and parts pass by the free lower end by slightly displacing it. The lower end then returns to its initial position to reform a curtain for effectively sealing the cabinet against the escape of particulate.
A problem often encountered with such seals is that they are subject to wear from the blast treatment process and must be frequently replaced. Another problem is that they must be made of sufficiently lightweight and flexible material that the parts to be treated can pass through the seals yet they must be sufficiently stiff so as to maintain an effective closure of the blast chamber opening. As will be observed, these requirements are somewhat contradictory and previous finger seal constructions had not been entirely satisfactory.
It is accordingly an object of the present invention to provide an improved finger seal which is both flexible and wear resistant to blast treatment.
It is another object of the invention to provide an improved finger seal which is formed of polyurethane material and includes a reinforced rib construction so that it is flexible yet strong.
Other objects and advantages of the invention will be apparent from the remaining portion of the specification.